On a general basis lithographic/metrology tools always comprise a base frame and a payload. The base frame is fastened to the floor or platform. The payload is a frame that supports the vibration sensitive components such as stages, beams, lenses, and measurement devices. Supporting devices are often located between the base frame and the payload. Insofar, generally, the supporting devices have at least a double functionality. They on the one side support the payload and on the other isolate it from vibrations. Vibrations of the base frame are caused by all kind of lithographic/metrology device self induced forces, such as stage reaction forces, acoustics, material-handling systems, tubes, and pumps. Since the base frame is placed on a floor or platform, vibration will also arise in the base under influence of vibrations present in the floor.
Such a lithographic device with the respective supporting devices is, for example, known from the U.S. Pat. No. 6,226,075.
The lithography device disclosed therein comprises a supporting device provided with a first part, a second part, and a gas spring for supporting the second part relative to the first part parallel to a support direction. The gas spring comprises a pressure chamber, which is provided in an intermediate part and is bounded by a piston which is displaceable in the intermediate part parallel to the support direction and is supported perpendicularly to the support direction by means of a static gas bearing. The stiffness of the supporting device parallel to the support direction is thus substantially entirely determined by the stiffness of the gas spring.
The supporting device of the known kind has the following disadvantages:                It is an open gas system, which is not leakage free. The static gas bearings need a continuous gas flow from the air supply unit.        This system needs to have ultra fine (<0.003 um) particle filter in order to overcome contamination of wafers and other contamination sensitive parts in the lithographic/metrology tool.        Without major changes on the known system, it is not usable in a vacuum application        The used gas bearings require high accurate parts (tolerances app. +/−1 μm)        Gas bearings are very sensitive for contamination.        